It sounds like your Tama was sick. Were there any poops around it in piles? Leaving your Tamagotchi alone with it's messes makes them sick and they can die from it if you don't treat them right away. You can't really select any icons other than the ones for flushing and for items.
Do you know where to play with your items? Go to the chest icon on the bottom icon row, and select it. The first option is medicine, select it. Sometimes, you need to use Medicine 2 or 3 times to heal your babies completely.
However, if none of the icons were working, at all, then I'm not sure what it was at all. Next time that this happens, try giving them medicine first.